Control for gas-powered motor



United States Patent Inventor Charles Passaggio Cheshire, Conn.

App]. No. 833,485

Filed June 16, 1969 Patented Dec. 22, 1970 Assignee Scovil Manufacturing Company Waterbury, Conn. a corporation of Delaware CONTROL FOR GAS-POWERED MOTOR 2 Claims, 4 Drawing Figs.

Int. Cl. F011 31/08 Field ofSearch 91/337,

346, 350(Cursory) {56] References Cited UNITED STATES PATENTS 375,200 12/1887 Ross 91/337 1,731,048 10/1929 Holmes et al. 91/337 2,057,364 10/1936 Bystricky.... 91/337 2,151,891 6/1956 Mohler 91/337 Primary Examiner-Paul E. Maslousky Attomey-Dallett lloopes ABSTRACT: A control valve for a reciprocating fluid motor comprises a ported body with a spool valve therein. A spool valve is driven by a drive sleeve through lost motion means. The drive sleeve is assisted by spring means engaging in indentations in the drive sleeve, positioned and'proportioned'so that the spring means is urging the spool valve onward when the valve is at its null points.

PATENTED UEC22 I970 INVENTOR. Charles Possoggio BY D 2 L ATTORNEY.

CONTROL FOR GAS-POWERED MOTOR This invention relates to a gas-powered motor of the reciprocating type in which the piston or other power element reciprocates the control valve to alternate the pressure side of the piston. More specifically, in such a motor this invention relates to control valve drive means especially structured to avoid hang-ups of the valve at the valve null points.

In the prior art there are gas-powered motors in which the control valve is moved by the motor so that the gas pressure or vacuum source is connected at the end of the stroke to the opposite side of the piston. An example is U.S. Pat. No. 1,731,048 to Holmes et al. In such devices of the prior art, a problem has been that the motor which may not be very strong can encounter sufficient friction in its movement to cause a slowing down of the control valve in the critical portion of travel during which the control valve opens or closes both power ports. This portion of travel is called the null point and at this point the same pressure, or absence of pressure, is working on both sides of this piston or the like so that the piston stalls and the motor stops. The motor can only be reactivated by manually moving the motor past thenull point.

In the above-mentioned patent, an attempt was made to avoid null point hang-ups by using a spring detent cooperating with a pair of circumferential grooves in the spool-type control valve. The spring detent serves to hold the spool valve in position until sufficient pressure is exerted by the driving spring against the spool valve to overcome the holding movement of the spring detent. It was believed that the spool valve, once moving, would not be likely to hang up at the null points.

It has been the experience with the arrangement discussed above, however, that because the circumferential grooves on the spool valve have inclined walls, the resistance to continued movement actually can be increased during such movement by the action of the spring detent on the inclined walls and thus null point hang-ups are still possible with the abovedescribed structure. I

Under the present invention, an improvement on the earlier structure now eliminates the possibility of null point hang-ups by interposing between the spool valve and the control rod a drive sleeve element against which the spring detent operates. The spool valve and the drive sleeve are so structured that the spool valve movement is not commenced until the drive sleeve has reached a point where its forward motion to the end of its travel is assured. Further, lost motion between the drive sleeve and the valve is such that the spring detent is working on a downhill slope when the valve is at the null point either on the upstroke or the downstroke.

Other objects and features of the invention will be clear from a review of the following specification including the drawings wherein:

FIG. 1 is a sectional view of a motor having a control embodying the invention;

' FIG. 2 is an enlarged sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is an enlarged fragmentary sectional view of a control embodying the invention and showing the control rod after the commencement of its downstroke; and

FIG. 4 is a fragmentary sectional view showing the control rod at its lowermost position.

Referring more specifically to the drawing, a motor embodying the invention is generally designated in FIG. 1. It comprises a housing 12 having a piston or diaphragm 14 power element in its power chamber. The piston may be connected through appropriate means to drive a pump 16 with which this invention is not concerned. In the version shown, the housing includes a control cavity 18 to which a vacuum source conduit 20 is connected. Passages 22 and 24 in the housing connect the control chamber respectively with the.

lower and upper compartments of the power chamber.

The control cavity as shown in FIG. 3 terminates in an open end of the housing and from this end into the cavity extends the cavity liner 26. The liner is formed with a plurality of Iongitudinally spaced outward circumferential flanges 28, 30, 32, and 34. The annular spaces between the circumferential flanges are aligned with the passages 22, 20 and 24 respectively, and ports 36, 38 and 40 are provided through the liner at their respective levels. A tubular spool valve element 42 is slideably disposed within the liner and has end flanges 44 and 46 spaced so that the indentation between the flanges permits port 38 to communicate with ports 36 and 40 depending on whether the spool element 42 is up or down.

A drive sleeve 48 is slideably disposed inside the liner and housing. At its lower end, the drive sleeve is slidably surrounded by the spool valve element 42. In FIG. 3, a shoulder 50 is formed on the drive sleeve to abut the upper end of the spool element. At the lower end, a stop ring 52 is disposed in an annular groove in the drive spool spaced from the shoulder 50 somewhat more than the length of the spool element for reasons which will be understood.

An upwardly facing internal shoulder 54 is formed in the drive spool and a downwardly facing shoulder 56 is spaced from and opposes the shoulder 54. In practice, the downwardly facing shoulder 56 may be'in the bottom end of the plug 58 secured in the upper end of the drive sleeve.

In the internal wall of the liner at a level above the housing there is formed a deep annular channel 60 which carries a garter spring 62. On the drive sleeve are formed spaced circumferential indentations 64 and 66 with a rounded peak 68 therebetween. The valleys of the indentations 64 and 66 are spaced apart a distance equal to the length of travel of the spool valve element 42 plus the lost motion space S shown between the stop ring 52 and the lower end of the valve element (FIG. 3). The compression the garter spring 62 is such that it urges the drive sleeve toward positions in which the garter spring engages the deepest part of the respective indentations 64 and 66.

Referring again to FIG. 1, the piston or diaphragm 14 is linked to an upwardly extending control rod 70. This rod is reduced adjacent its upper end to receive a pair of opposed sliding bushings 72 and 74. A nut 76 is secured to the threaded upper end of the rod. An axial spring 78 is disposed between the flanges of the bushings.

In operation, as shown in FIG. 3, with the piston and control rod 70 on its down stroke, the bushing 72 bears against shoulder 54 and urges the drive rod downwardly against the force of the garter spring. When sufficient pressure is exerted by the spring 78 on the bushing, the upper inclined surface of the indentation 64 will cause the garter spring 62 to expand and the downward movement of the drive sleeve will commence. In this critical portion of travel, during which the ex pansion of the garter spring 62 has commenced, there is no movement of the spool element 42 from its upper position because the space S which provides lost motion between the drive sleeve 48 and the spool 42 had been, prior to the position shown in FIG. 3, between the upper flange 44 and the shoulder 50. This lost motion permits the drive sleeve 48 to get a running start through the most critical inhibition period of the spring 62 prior to any movement of the spool valve. Thus, once the drive sleeve has contacted the spool element, all likelihood of the drive sleeve stalling out due to the inhibiting force of the spring 62 has passed and thus the spool valve will not become hung up at the null point with its flanges44 and 46 overlying the ports 36 and 40 equally to stall the mo-- tor. Further, when the spool seals are at the point where they block the valve ports, that is, the valve is at the null point, the dimensions of the parts are such that cam peak 68 is lower than the level of the centerline of the garter spring. The result is that the spring, working against the inwardly inclined cam surface of the undersection 66 urges the valve past the null point.

It will be understood that at the commencement of the upstroke, the situation is reversed. The drive sleeve will have moved up with the garter spring well up the incline of depression 66 prior to the space S closing as the drive sleeve moves up. When the valve is at the null point, the garter spring is working against the inwardly inclined cam surface of the indentation 64 and urges the valve past the null point. This action of the spring in avoiding hang-ups of the valve at the null point in either the upward or the downward stroke is made possible by the lost motion between the drive sleeve and the spool valve element.

By virtue of the structure shown, the likelihood of null point hang-ups inherent in the earlier devices of this type is eliminated.

Iclaim:

l. A gas-powered, self-reciprocating motor having a housing with a power element therein operated on opposite sides alternately by gas under greater pressure, the power element driving a control rod extending into a control cavity in the housing, a drive sleeve reciprocal in the control cavity and surrounding the end of the rod and reciprocable longitudinally of the cavity by lost motion means moved by the control rod as the rod reciprocates, the drive sleeve being formed with a pair of longitudinally spaced indentations, spring-pressed means v stationed in the side of the cavity and extending alternately into said indentations as the drive sleeve reciprocates, the indentations having sloping walls so that once the sloping wall of the approaching indentation is opposite and engaged by the spring-pressed means the movement of the drive sleeve in the direction of the approaching indentation is assisted, and a spool valve element operable as it reciprocates in the cavity with passages in the housing to communicate power fluid alternately to the opposite sides of the piston, the spool valve element being driven in reciprocation by the drive sleeve through lost motion means, so that the spool valve element is not moved until the drive sleeve has moved so that springpressed means is well past the bottom of the indentation in whichvit was most recently engaged and when the valve is at the null point the spring-pressed means is on a level with the inwardly inclined wall of the approaching indentations.

2. A motor as described in claim 1 in which the springpressed means is a garter spring disposed partly in a circumferential groove in the control cavity. 

